Radio receiver



' Nav. 26, 194%. G. w. FYLER v ,709

RADIO RECEIVER Filed Nov. 2, 1938 Inventor: Geor%e W. Fyler:

by Wan 1 7 His/\tborhey.

Patented Nov. 26, 1940 UNITED STATES-*- RADIO RECEIVER George W. Fyler,Stratford, Conn rassignorc to. General Electric Company, A a corporationoff" NewYork Application November 2, 193s;-se1:ia1 Nm,23s;417

Myv invention relates to radio receivers and particularlyv to suchreceivers employing loop antennae.

In copending applications Serial No. 211,428

6 of Arthur G. Manke, filed June 2, 1938, entitled Signal system, andassigned to the same assignee asmy, present application, is shown aradio receiver employing both a loop antenna and also a vertical antennasuch as the usual outdoor antenna used in connection with ordinaryhousehold receivers. Switching means are employed alternately to connectthe loop and the vertical antenna to the receiver. Such receivers haveproven highly popular for home use and one of the objects of my presentinvention is tosimplify its structure and to reduce the cost of itsmanufacture.

Aifurther object of my invention is to provide means whereby the inputtransformer commonly used between the receiving vertical antenna andreceiver is eliminated and whereby the vertical antenna may be employed,and adapted for optional use, by adding to the receiver only a minimumnumber of circuit elements'over those required'for use of the loop forreception. Such simplification of the receiver is highly desirableespecially'in such a receiver in which the loop ismainly, employed asthe receptor of the system.

A further object of the invention is to effect such simplification and,at the same time, to provide means whereby the vertical antenna iseffectivein all bands or only certain bands as desired.

The novel features which I believe to becharacteristic of my inventionareset forth with particularity in the appended claims. My inventionitself however, both as to its organization and method of operationtogether with further ob-' jects and advantages thereof may best beunder- 4o; stood by reference to the following description taken inconnection with the accompanying drawing in which the single figurerepresents the embodiment of my invention.

Referring to the drawing I have shown at I an antenna of the so-calledvertical type. When I. speak of a vertical antenna I have reference tothe ordinary capacitive antenna such as is commonlyused in connectionwith household receivers and which commonly are mounted in an 50 Jelevated position out of doors.

At 2 I have conventionally represented a loop antenna. This loop may bethe type shown in the above referred to Manke application and-nonconducting support and which is housed bod- (Cll 250 211) end.'.wallwhereby "the: flow of;currents inthe; o

shield comprising suchzconductors isfsubstan- I tially prevented while.the shield :at. the. same timeoperatessiefficientlyielectrostaticallyto shield the loopcZ; Thiszloop2, issalso arranged to be orientedpaszby.rotationvwith the shield asaunit,

toza direction in which'thereception .of undesired noiseicurrentsis aminimum.

This loop as shown in the drawing is connected betweenground at 5 andthegrid of an electron discharge device 6. through :a pair of switches 1and:.8,--the,cathode;of the discharge device being grounded. at 9; Itistuned to a desiredfre quency bymeans of a condenser Ill;

The electron discharge device G'maybe the first stage of a radioreceiver, and may comprise 25- a radio frequency amplifier or theconventional superheterodyne converterof the system. Only its grid andcathode are shown but'it will of course be understood that thisdischargedevice is of any suitable type used for the purpose 30v mentioned..

Condenser Ill may beothe usual uni-control condenser of the ordinarytuned radio frequency or superheterodyne radio receiver. If the receiver be one of the tuned radio frequency type this. condenser isuni-controlled with the. condensers in the input circuit of the otheramplifiers in the cascade connection. If the receiver be one ofthe-superheterodyne type this condenser is uni-controlled with thetuning, con- 40 denserof the-local oscillator and with such othervariably, tuned radiovfrequency circuits as may be employed in thereceiver. One such condenser isv indicated at l0.

Switches 1 and 8 are the conventional band change switches of thereceiver and are arranged asindicated by the dotted line H, foruni-control-movement through three positions. These positions areindicated bythe letters B, C and. D as applied to the two switches. thedrawing, these switches are in their position B in which the loop 2 isconnected between the grid. and cathode of the discharge device. This isthe position in which the receiver is arranged a for operation inthe-usual broadcast range of T= As shown in 5 y antenna is desirable.

frequencies, this range extending from 550 kilocycles to 1500kilocycles.

For operation of the receiver in a higher frequency band, switches I and8 may be operated to position C. In this position the antenna I isconnected through switch 1 and a winding l2 to ground. This winding I2is the primary winding of a transformer having a secondary winding l3,which is connected through switch 8 between the grid and cathode of thedischarge device, and which is tuned by the condenser III to thereceived frequency, condenser M of course being the usual trimmercondenser, which is connected across the secondary winding. I

If a still higher band of frequencies is to be received switches 1 and 8may be operated to position D thereby connecting winding l5 between theantenna and ground and winding, l6

between the grid and cathode of the discharge device, these windingsbeing respectively the primary and secondary windings of a transformeradapted for operation in a still higher frequency band. It is tuned tothis still higher frequency by condenser l0 and is trimmed in the usualWay by trimmer condenser II.

A further switch 20 is shown as having two positions. In the positionillustrated it connects the antenna 1 to the shield 3 of the loop, oneterminal of the loop 2 being also connected to the shield. At theopposite position of the switch the antenna is connected to anintermediate point 2! on the loop 2 and currents in it thus flow throughthe lower portion of the loop 2 to ground. In this way these currentsare transformed by means of the loop 2 acting as an autotransformer andare caused to induce voltages between the grid and cathode of thedischarge device.

The purpose of switch 20 may, of course, be served by mere clipsarranged within the receiver to which the antenna may be connected wheninstalled, but if desired, may comprise a double-throw switch arrangedfor convenient manual operation.

With switch 20 in the position shown the antenna and shield areconnected to ground and thus are ineffective to intercept radio waves inspace. The shield, of course, operates electrostatically to shield theloop 2 and thus reduce reception of undesired noise current.

It may occur, however, in a particular installation that noise currentsare not suificiently intense to be the predominant consideration andthat the stronger reception from the vertical This may be effectedmerely by operating switch 20 to the upper position whereby the loop 2acts as a step-up transformer between the vertical antenna I and thecircuit of the discharge device. By utilizing this loop as the inputtransformer the necessity for a separate input transformer for usebetween the antenna and the input of the discharge device for receptionof frequencies in the broadcast band is avoided. By properly choosingthe point 21 upon the loop 2 very desirable reception may be had withoutdisturbing the tuning of the loop. If the intermediate point be chosentoo far removed from the grounded end of the loop the capacity of theantenna may so effect the input circuit of the discharge device 6 thatits tuning may no longer be controlled by the uni-control condensers ofthe set. That is, the so-called tracking of the uni-control condensersis not satisfactory. I have found, however, that very satisfactoryoperation of the loop as a transformer may be had without materialdisturbance of the tuning of the loop over the broadcast band by chosingthe point 2| relatively close to the grounded end of the loop.

With switches I and 8 in the 0 position the circuit of the loop isopened at switch 8 and the loop, with its shield 3, and antenna I alloperate as a. vertical capacitive antenna in the higher frequency band.This is also true when switches l and 8 are in the position D.

It is thus seen that with switch 20 in the position shown the antenna lis ineffective in the B band but is effective in bands C and D. Antennal is effective in all bands when switch 20 is in the upper position.

It may happen, however, that reception at a certain frequency in one ofthe higher frequency bands, when switch 20 is in its upper position, isrendered unsatisfactory by reason of resonance of the loop at theparticular frequency. In one practical installation it was found thatreception was unsatisfactory for this reason, at 12 megacycles, whichwas a frequency in the D band of frequencies to be received. To avoidthis difficulty switch 8 may be provided with a stationary contact 22and a movable contact 23 connected and arranged to short circuit theloop when the band switch I, 8 is adjusted for operation in the D band.This movable contact, which is actuated by the armature of switch 8bridges contacts B and 22 when the switch is in the D position therebyshort circuiting the loop and rendering the vertical antenna effectiveirrespective of any resonance in the loop itself. i

While I have shown a particular embodiment of my invention it will ofcourse be understood that I do not wish to be limited thereto sincedifferent modifications may be made and I anticipate by the appendedclaims to cover any such modifications as fall within the true spiritand scope of my invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. The combination, in a radio receiver of an electron discharge devicehaving a grid and cathode, a loop antenna connected between said gridand cathode to supply signals intercepted by said loop to said electrondischarge device, one side only of said loop antenna being grounded, anda vertical antenna connected to an intermediate point on said loop nearthe grounded end thereof whereby additional energy is intercepted bysaid vertical antenna and supplied through said loop to said dischargedevice, the portion of the loop between said intermediate point andground acting to induce electromotive force received on the verticalantenna into the circuit of said loop and discharge device.

2. The combination, in a radio receiver, of an electron discharge devicehaving a grid and cathode, a loop antenna having terminals connectedrespectively to said grid and cathode, the terminal of said loop antennaconnected to said cathode being grounded, the other terminal beingeffectively ungrounded and a vertical antenna connected to anintermediate point on said loop whereby energy is received from both theloop and vertical antenna, means to tune said loop over a range offrequencies, said intermediate point being chosen sufiiciently close tothe grounded end of said loop to prevent material disturbance of thetuning of said loop by the i capacity of said vertical antenna. whileproducing materially increased reception due to step-up transformeraction in said loop between the circuit of said vertical antenna and thecircuit of said loop.

3. The combination in a multiband radio receiver, of an antenna, anelectron discharge device, a transformer connected between said antennaand discharge device and tuned by a condenser for operation over acertain frequency band, a loop, switching means to disconnect saidtransformer from said antenna and discharge device and to connect saidloop to said discharge device and condenser, said condenser beingadapted to tune said loop over a different frequency band, and means toutilize said loop to transform electromotive forces received on saidantenna in said different frequency band and to supply saidelectromotive forces to said discharge device.

4. The combination, in a multiband radio receiver of an antenna, anelectron discharge device, a condenser, a transformer connected betweensaid antenna and discharge device and tuned by said condenser foroperation in a certain frequency band, a loop adapted for operation in adifferent frequency band, switching means to disconnect said transformerfrom said antenna, discharge device, and condenser, and to connect saidloop to'said discharge device, and condenser, said condenser beingadapted to tune said loop and means to connect said antenna to anintermediate point on said loop.

5. The combination, in a multiband receiver, of an antenna, aloop, meansto connect said loop to said receiver for reception in a certainfrequency band and to connect said antenna to said receiver through acoupling device for reception only in another frequency band, additionalmeans to connect said antenna to said receiver through said loop forreception therefrom in said certain frequency band Whensaid loop is alsoutilized for reception, and a tuning condenser connected to produceresonance with said loop in said certain frequency band and with saidcoupling device in said other frequency band.

6. The combination, in a multiband receiver, of an antenna, a loop,means to connect two terminals of said loop in circuit with saidreceiver for reception of waves intercepted by said loop havingfrequencies in a certain range, means to couple said loop to saidreceiver for operation in a different range, means to connect saidantenna to said receiver through said loop for reception in a differentfrequency range, and,

means to short circuit said loop to prevent resonance in the loop frominterfering with reception in said different frequency range.

7. The combination, in a radio receiver of an electron discharge devicehaving a grid and a cathode, said cathode being connected to ground, aloop antenna having one terminal connected to said grid and the otherterminal connected to said cathode, a variable condenser connectedacross said loop, a second tuned circuit in said receiver including acondenser, said condenser being unicontrolled to vary the tuning of saidcircuit and said loop in alignment with each other, and means toincrease reception of energy by said receiver, said means comprising a.capacitive antenna connected to an intermediate point on said loop, saidintermediate point being positioned sufficiently far from said' terminalconnected to said cathode materially to increase reception of radiantenergy but insufficiently far to cause the tuning alignment of said loopand tuned circuit upon. unicontrolled variation of said condensers'to bedisturbed by the capacitance of said capacitive antenna.

8. In combination, an electron discharge device, having a grid andcathode, a loop antenna connected between said grid and cathode, saidloop antenna being arranged for orientation for minimum response toundesired noise currents, a capacitive antenna having substantiallyuniform response in all directions, and means alternatively to connectsaid capacitive antenna to ground through a portion of said'loop substantiallyexclusively to other portions of said loop, whereby currentsintercepted by said capacitive antenna are supplied to said dischargedevice through auto transformer action GEORGE W. FYLER.

of said loop thereby producing reception from

